Method for adding heat to a reactor system used to convert oxygenates to olefins

ABSTRACT

The present invention provides a method for adding heat to a reactor system used to convert oxygenates to olefin, in which supplemental heat is added with a heating fuel, e.g., a torch oil, having low autoignition temperature, low sulfur, and low nitrogen content.

REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.10/422,924, filed Apr. 24, 2003, and now U.S. Pat. No. 6,768,036, whichis a Continuation-in-Part of U.S. application Ser. No. 10/152,908 filedMay 22, 2002, now abandoned which claims the benefit of and is aContinuation-in-Part of U.S. application Ser. No. 60/345,681, filed Dec.31, 2001.

FIELD OF THE INVENTION

The present invention relates to a method for converting a feedincluding an oxygenate to a product including a light olefin, in whichsupplemental heat is added with a heating fuel having low autoignitiontemperature, low sulfur, and low nitrogen content.

BACKGROUND OF THE INVENTION

Light olefins, defined herein as ethylene, propylene, butylene andmixtures thereof, serve as feeds for the production of numerousimportant chemicals and polymers. Particularly, light olefins are usedin the manufacture of polyolefins such as polypropylene andpolyethylene. Catalysts for polyethylene and polypropylene require aproduct that is substantially free of contaminants such as sulfur andnitrogen. When sulfur and nitrogen compounds are present in the olefinfeedstock, the catalyst is rendered less effective resulting in poorerquality goods or less efficient polymerization products.

One emerging technology for the production of light olefins usesoxygenate feedstocks such as methanol, ethanol or dimethyl ether.Methanol, ethanol and dimethyl ether feedstocks are produced fromsynthesis gas derived from natural gas or other sources. Oxygenatefeedstocks produced from this method are desirable because they containnegligible amounts of nitrogen or sulfur and result in olefin productsthat are less poisonous to polymerization catalysts. One embodiment ofthe reaction of oxygenates to olefins uses a molecular sieve catalyst,such as a SAPO catalyst, in a reactor system that has an oxygenate toolefin (“OTO”) reactor and a catalyst regenerator. The catalyst in theOTO reactor converts oxygenates to olefins and also generates anddeposits carbonaceous material (coke) on the molecular sieve catalystsused to catalyze the conversion process. Over accumulation of thesecarbonaceous deposits will interfere with the catalyst's ability topromote the reaction. Thus, the molecular sieve catalyst is periodicallyrecycled to the catalyst regenerator. During regeneration, the coke isremoved from the catalyst by combustion with oxygen, which restores thecatalytic activity of the catalyst. The regenerated catalyst is thenrecycled back to the OTO reactor where it is reused to catalyze the OTOreaction.

U.S. Pat. Nos. 6,023,005 and 6,166,282, both of which are incorporatedherein by reference, disclose methods of producing ethylene andpropylene by catalytic conversion of oxygenate in a fluidized bedreaction process which utilizes catalyst regeneration.

U.S. Pat. Nos. 4,595,567, and 4,615,992, both of which are incorporatedherein by reference, disclose general and specific regeneration devicesand techniques.

The reactor system comprising an OTO reactor and a regenerator oftenrequires the addition of heat to the reactor system. The OTO reaction isexothermic, requiring an initial heating to initiate the reaction, afterwhich it is self-sustaining. There are also periods where the oxygenatefeed must be interrupted, at which time it would be desirable to keepthe reactor and regenerator hot. In addition, the initial start-up ofthe regenerator and heating of the catalyst also requires heat.

Conventionally, the regenerator apparatus is preheated by an auxiliaryburner which burns a starting fuel such as natural gas with air toprovide a heated gas that contains air and gaseous combustion productssuch as carbon dioxide and water (steam), to the regenerator. Theauxiliary burner can be associated with the regenerator air blower thatintroduces the heated gas through an air inlet at the bottom of theregenerator. However, given the low heat capacity of such heated gas,resulting in part from its expansion upon heating, the heat input to theunit is limited. Particularly, the maximum amount of heat and themaximum temperature is limited. When heat is added to reactors otherthan OTO reactor systems, such as a fluid catalytic cracking (FCC)system, hydrocarbon feed (gas oil) to the FCC unit is burned in theregenerator to heat the catalyst. However, the gas oil feedstock of anFCC unit is contaminated with nitrogen and sulfur and would beunsuitable in an OTO process, as the gas oil would increase the levelsof these contaminants in the products. Methanol is undesirable as a fuelfor heating catalyst because it has a high autoignition temperature, andigniting and sustaining the burning of methanol would be difficult. Theprocess of fluid catalytic cracking (FCC) normally circulates hotcatalyst from the regenerator to the reactor to add heat to the reactor.One method of doing this combusts a fuel with the air feed to theregenerator. The FCC process normally uses fuel gas (including naturalgas), or a combination of fuel gas and heavy liquid feedstock for thispurpose. The fuel gas is combusted in an auxiliary burner, located afterthe air blower but before entering the fluidized bed of catalyst in theregenerator. The limited heat capacity of the regeneration air,resulting in part from its expansion upon heating, limits the rate atwhich heat is added to the regenerator through this method. It isnormally desirable to add heat at a greater rate, and thus a liquidfuel, normally consisting of gas oil feedstock, is added to thefluidized catalyst zone. The catalyst has a much higher heat capacitythan the combustion air, and thus liquid fuel can be added at a muchgreater rate in the fluidized catalyst zone than can be added to thecombustion air through the auxiliary burner. The gas oil also has arelatively low autoignition temperature of 315–370° C. (600–700° F.),which aids in the initiation of combustion, as well as helping to ensurethat the combustion will not be extinguished during a low temperatureexcursion.

In trying to adapt the FCC heating method to the MTO process, some majorproblems are encountered. Gas oil cannot be used as the heating fuel,because the sulfur and nitrogen introduced by the gas oil cannot betolerated in the MTO product recovery section. The MTO feedstock,methanol, cannot be used as the heating fuel, because its autoignitiontemperature of 468° C. (875° F.) is so high that preheating the catalystbed in the regenerator to a sufficient temperature to initiate thecombustion of methanol is difficult. Also, there is a greater risk ofextinguishing the burn from a low temperature excursion.

Accordingly, it would be desirable to provide a process for makingolefins from oxygenate which has an initiation procedure which providesa high heat input to an oxygenate to olefins reactor system within areasonable time, hours rather than days, to provide supplemental heat tothe reactor, without contaminating either the OTO catalyst or the MTOproducts and byproducts. The present invention satisfies these and otherneeds.

SUMMARY OF THE INVENTION

The present invention solves the current needs in the art by providing amethod for converting a feed including an oxygenate to a productincluding a light olefin.

The method of the present invention is conducted in a reactor apparatus.As used herein, the term “reactor apparatus” refers to an apparatuswhich includes at least a place in which an oxygenate to olefinconversion reaction takes place. As further used herein, the term“reaction zone” refers to the portion of a reactor apparatus in whichthe oxygenate to olefin conversion reaction takes place and is usedsynonymously with the term “reactor.” Desirably, the reactor apparatusincludes a reaction zone, an inlet zone and a disengaging zone. The“inlet zone” is the portion of the reactor apparatus into which feed andcatalyst are introduced. The “reaction zone” is the portion of thereactor apparatus in which the feed is contacted with the catalyst underconditions effective to convert the oxygenate portion of the feed into alight olefin product. The “disengaging zone” is the portion of thereactor apparatus in which the catalyst and any additional solids in thereactor are separated from the products. Typically, the reaction zone ispositioned between the inlet zone and the disengaging zone.

The present invention relates to a process for making an olefin productfrom an oxygenate feedstock in the presence of an oxygenate to olefinmolecular sieve catalyst which comprises:

-   a) contacting at least a portion of the catalyst with a regeneration    medium in a regeneration zone;-   b) heating said regeneration zone to a first temperature of at least    225° C. (437° F.), e.g., at least 260° C. (500° F.),-   c) feeding to said regeneration zone a heating fuel having an    autoignition temperature less than the first temperature and    containing less than 500 wppm sulfur, e.g., less than 100 wppm    sulfur, and less than 200 wppm nitrogen, e.g., less than 100 wppm    nitrogen, thereby causing the heating fuel to ignite and provide a    heated catalyst; and-   d) circulating said heated catalyst to the reaction zone; and-   e) additionally contacting the feedstock in a reaction zone with    said oxygenate to olefin molecular sieve catalyst including said    heated catalyst, under conditions effective to convert the feedstock    into an olefin product stream.

In one embodiment, the olefin product stream comprises C₂–C₃ olefins.

In still another embodiment of the invention, the conditions employedare effective to form carbonaceous deposits on the catalyst.

In still another embodiment, the catalyst is heated to at least 316° C.(600° F.) in the regeneration zone prior to the step of feeding theheating fuel.

In yet another embodiment of the invention, the regeneration zone has afuel inlet and an air inlet capable of providing an airflow through theregeneration zone, located upstream from the fuel inlet in relation todirection of the airflow, and the process further comprises (1)combusting a starting fuel with an air stream from said air inletthereby imparting sufficient heat content within the regeneration zoneto obtain the first temperature at or near the fuel inlet and (2)feeding the heating fuel through the fuel inlet.

In still another embodiment, the starting fuel employs a carbonaceousgas, e.g., natural gas.

In yet another embodiment of the invention, the starting fuel has anautoignition temperature of greater than about 482° C. (900° F.).

In another embodiment, the process of the invention further comprisesfilling the regeneration zone with the catalyst to a level sufficient tocover said fuel inlet before the combusting step (1), and addingadditional catalyst after step (2) of feeding the heating fuel, toprovide additional heated catalyst.

In still another embodiment, the catalyst is heated to at least 316° C.(600° F.) in the regeneration zone prior to the feeding step (2). heatedto at least 316° C. (600° F.)

In another embodiment, the heating fuel is a liquid fuel.

In still another embodiment, at least 50 wt % of the heating fuel is aC₁₁–C₂₀ hydrocarbon fraction.

In another embodiment, at least 75 wt % of the heating fuel is a C₁₁–C₂₀hydrocarbon fraction.

In still another embodiment, at least 85 wt % of said heating fuel is aC₁₁–C₂₀ hydrocarbon fraction.

In another embodiment, at least 75 wt % of the heating fuel is a C₁₂–C₁₉hydrocarbon fraction and further said heating fuel has an autoignitiontemperature ranging from 232°–271° C. (450°–520° F.) and contains lessthan 10 wppm sulfur and less than 10 wppm nitrogen.

In yet another embodiment, at least 75 wt % of the heating fuel is a C₁₂to C₁₆ hydrocarbon fraction.

In another embodiment, at least 75 wt % of the heating fuel is a C₁₂ toC₁₄ hydrocarbon fraction.

In still another embodiment, the reaction zone is cooled by steaminjection.

In another embodiment, the reaction zone comprises a riser.

In yet another embodiment, the reaction zone comprises plural risers.

In still yet another embodiment, the reaction zone has two risers.

In yet another embodiment, the catalyst comprises molecular sieve havinga pore diameter of less than 5.0 Angstroms.

In still yet another embodiment, the catalyst comprises at least onemolecular sieve framework-type selected from the group consisting ofAEI, AFT, APC, ATN, ATT, ATV, AWW, BIK, CAS, CHA, CHI, DAC, DDR, EDI,ERI, GOO, KFI, LEV, LOV, LTA, MON, PAU, PHI, RHO, ROG, THO, ZSM-5,ZSM-4, SAPO-34, SAPO-17, SAPO-18, MeAPSO and substituted groups thereof.

In yet another embodiment, the catalyst comprises a molecular sievehaving a pore diameter of 5–10 Angstroms.

In still yet another embodiment, the catalyst comprises at least onemolecular sieve framework-type selected from the group consisting ofMFI, MEL, MTW, EUO, MTT, HEU, FER, AFO, AEL, TON, and substituted groupsthereof.

In another embodiment, the heating step (b) occurs before the contactingstep (e).

In still another embodiment, the heating step (b) occurs concurrent withthe contacting step (e).

In yet another embodiment, first contacting step (a) occurs before theheating step (b).

In still another embodiment, the heating fuel contains less than 10wppm, e.g., less than 5 wppm, sulpher and less than 10 wppm, e.g., lessthan 5 wppm, nitrogen.

In yet another embodiment, the invention relates to a method of addingheat to a reactor system having an oxygenate to olefin reaction zone anda catalyst regeneration zone wherein catalyst is cycled from thereaction zone to the regeneration zone and from the regeneration zone tothe reaction zone, the method comprising:

-   -   fluidizing catalyst in the regeneration zone in the presence of        an oxygen containing gas;    -   heating the catalyst in the regeneration zone to a first        temperature;    -   introducing a heating fuel into the regeneration zone wherein        the heating fuel has about 100 wppm or less of sulfur and has        about 100 wppm or less nitrogen and an autoignition temperature        greater than the first temperature but no greater than about        482° C. (900° F.) to provide a heated catalyst; and    -   provide the heated catalyst into the reaction zone.

In yet another embodiment of the invention described immediately above,the process further comprises: contacting the catalyst with an oxygenatefeedstock under conditions sufficient to convert said oxygenate to anolefin-rich product.

In still another embodiment of the invention described immediatelyabove, the invention further comprises the process wherein said heatingfuel contains a total of no greater than 20 wppm of metal selected fromthe group consisting of nickel and vanadium.

In yet another embodiment, the invention relates to a process forinitially increasing the temperature of a reactor system for making anolefin product from an oxygenate feedstock in the presence of anoxygenate to olefin molecular sieve catalyst which process comprises:

-   a) contacting at least a portion of the catalyst with a regeneration    medium in a regeneration zone;-   b) heating said regeneration zone to a first temperature of at least    225° C. (437° F.),-   c) feeding to said regeneration zone a heating fuel having an    autoignition temperature less than the first temperature and    containing less than 100 wppm sulfur and less than 100 wppm    nitrogen, thereby causing the heating fuel to ignite and provide a    heated catalyst; and-   d) circulating said heated catalyst to the reaction zone.

In still another embodiment of the invention described immediatelyabove, the invention comprises the process which further comprises:

-   e) additionally contacting the feedstock in a reaction zone with    said oxygenate to olefin molecular sieve catalyst including said    heated catalyst, under conditions effective to convert the feedstock    into an olefin product stream.

These and other advantages of the present invention shall becomeapparent from the following detailed description, the attached FIGUREand the appended claims.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE provides a diagram of a reactor apparatus comprising a highvelocity fluid bed with catalyst recirculation, and a regenerator havingan inlet for introducing a heating fuel for initial heat-up of thereactor.

DETAILED DESCRIPTION OF THE INVENTION

As noted above, the conversion of oxygenate feedstock to olefins is anexothermic reaction. Once initiated, the reaction can sustain itselfwithout the addition of external heat. However, there are certaincircumstances in which is it necessary to add heat to thereactor/regenerator system above that generated by the conversion ofoxygenate feedstock to olefins reaction. Examples include initialdry-out of the refractory linings of the reactor and regenerator system,initial preheating of the reactor prior to introduction of the oxygenatefeedstock, and maintaining reaction temperature during short-termoutages of the oxygenate feedstock.

The process of the present invention accomplishes this by addingsupplemental heat to the regenerator by the addition of a heating fueldirectly into the fluidized bed of catalyst. The fluidizing air providesthe oxygen for the combustion of the heating fuel. The fluidizedcatalyst particles are well mixed and have sufficient heat capacity toevenly distribute the heat generated from the combustion of the heatingfuel throughout the fluidized bed in the regenerator, resulting in arelatively uniform temperature within the regenerator bed. In oneembodiment, this hot catalyst can be circulated to the reactor, whereheat from the catalyst is transferred to the reactor. The catalyst coolsas it flows through the reactor, and is then returned to the regeneratorwhere it is re-heated. This method of adding heat can be used to dryrefractory in the reactor, to preheat the reactor prior to addition ofthe oxygenate feedstock, and/or to maintain reaction temperature duringoutages of the oxygenate feedstock.

The heating fuel must have certain critical properties to be useful inthe process of converting oxygenates to olefins. The autoignitiontemperature must be relatively low, no greater than about 454° C. (850°F.), in order to facilitate ignition of the heating fuel, and to ensurethat the combustion will not be extinguished in the event of a lowtemperature excursion. Also, it must have low sulfur and nitrogencontent, to prevent the introduction of these contaminants to thecatalyst or product recovery train. The heating fuel can contain metalimpurities (for example, nickel and/or vanadium) in amounts no greaterthan 100 wppm total metals, preferably no greater than 20 wppm totalmetals. In a preferred embodiment, the heating fuel can be a normallyliquid fuel, e.g., a hydrocarbonaceous liquid fuel.

When converting oxygenates to a light olefin product in a reactorapparatus comprising a fluidized bed of catalyst and a regenerator forthe catalyst, it is desirable to initiate operation of the apparatus byheating the reactor and catalyst to an operating temperature prior toaddition of oxygenate feedstock. The process of the present inventionaccomplishes this, in one embodiment, by heating the regeneration zoneby combusting a starting fuel, preferably a gaseous carbonaceous fuel,such as light gas or natural gas, with an air stream at or upstream ofthe regenerator air inlet. A portion of the oxygenate conversioncatalyst is added to the regeneration zone to a level sufficient tocover the fuel inlet of the regenerator. In one embodiment, the catalystin the regeneration zone is heated to a temperature of at least 225° C.This imparts sufficient heat content within the regeneration zone toinitiate and sustain ignition of a heating fuel that is then introducedat a rate sufficient to achieve a temperature sufficient to convertoxygenate to olefins upon contact with the catalyst. In one embodiment,the heating fuel is a normally liquid fuel comprising a C₁₁–C₂₀hydrocarbon fraction having an autoignition temperature less than 482°C. (900° F.) and containing less than 200 wppm sulfur and less than 500wppm nitrogen as elemental species, i.e. (S or N). The heating fuel isfed through the regenerator fuel inlet to the heated regeneration zoneand ignites under appropriate temperature conditions in the regenerator,resulting in heating of the catalyst. Additional catalyst can be addedalong with the heating fuel as needed, to the heated regeneration zone.The resulting heated catalyst is circulated to the reaction zone. In oneembodiment the circulation of the catalyst heats the reaction zone to areaction zone temperature of at least 316° C. (600° F.) which issufficient to effect catalytic conversion of oxygenates to olefins.Optionally, the catalyst in the reaction zone is circulated back to theregeneration zone.

In the process of one embodiment, a feed, including an oxygenate and anydiluents, is contacted in a reactor, or a reaction zone, with a catalystat effective process conditions so as to produce a product includinglight olefins. These process conditions include an effectivetemperature, pressure, WHSV (weight hourly space velocity), gassuperficial velocity and, optionally, an effective amount of diluent,correlated to produce light olefins. These process conditions aredescribed below in detail.

Desirably, the rate of catalyst, comprising molecular sieve and othermaterials such as binders, fillers, etc., recirculated to contact thefeed is from about 1 to about 100 times, more desirably from about 10 toabout 80 times, and most desirably from about 10 to about 50 times thetotal feed rate of oxygenates to the reactor. Desirably, a portion ofthe catalyst, comprising molecular sieve and any other materials such asbinders, fillers, etc., is removed from the reactor for regeneration andrecirculation back to the reactor at a rate of from about 0.1 times toabout 10 times, more desirably from about 0.2 to about 5 times, and mostdesirably from about 0.3 to about 3 times the total feed rate ofoxygenates to the reactor.

The temperature useful to convert oxygenates to light olefins variesover a wide range depending, at least in part, on the catalyst, thefraction of regenerated catalyst in a catalyst mixture, and theconfiguration of the reactor apparatus and the reactor. Although thepresent invention is not limited to a particular temperature, bestresults are obtained if the process is conducted at a temperature fromabout 316° C. to about 700° C., desirably from about 316° C. to about600° C., and most desirably from about 316° C. to about 500° C. Lowertemperatures generally result in lower rates of reaction, and theformation rate of the desired light olefin products typically becomemarkedly slower. However, at temperatures greater than 700° C., there isthe possibility that the process will not form an optimum amount oflight olefin products, and the rate at which coke and light saturatesform on the catalyst becomes too high.

Light olefins will form—although not necessarily in optimum amounts—at awide range of pressures including, but not limited to, autogeneouspressures and pressures from about 0.1 kPa to about 100 MPa. A desiredpressure is from about 6.9 kPa to about 34 MPa and most desirably fromabout 20 kPa to about 500 kPa. The foregoing pressures do not includethat of a diluent, if any, and refer to the partial pressure of the feedas it relates to oxygenate compounds and/or mixtures thereof. Typically,pressures outside of the stated ranges are used and are not excludedfrom the scope of the invention. In some circumstances, lower and upperextremes of pressure adversely affect selectivity, conversion, cokingrate, and/or reaction rate; however, light olefins will still form and,for that reason, these extremes of pressure are considered part of thepresent invention.

The process of the present invention is continued for a period of timesufficient to produce the desired light olefins. A steady state orsemi-steady state production of light olefins is attainable during thisperiod of time, largely determined by the reaction temperature, thepressure, the catalyst selected, the amount of recirculated spentcatalyst, the level of regeneration, the weight hourly space velocity,the superficial velocity, and other selected process designcharacteristics.

A wide range of WHSV's for the oxygenate conversion reaction, defined asweight of total oxygenate to the reaction zone per hour per weight ofmolecular sieve in the catalyst in the reaction zone, function with thepresent invention. The total oxygenate to the reaction zone includes alloxygenate in both the vapor and liquid phase. Although the catalystoften contains other materials which act as inerts, fillers or binders,the WHSV is calculated using only the weight of molecular sieve in thecatalyst in the reaction zone. The WHSV is desirably high enough tomaintain the catalyst in a fluidized state under the reaction conditionsand within the reactor configuration and design. Generally, the WHSV isfrom about 1 hr⁻¹ to about 5000 hr⁻¹, desirably from about 2 hr⁻¹ toabout 3000 hr⁻¹, and most desirably from about 5 hr⁻¹ to about 1500hr⁻¹. For a feed comprising methanol, dimethyl ether, or mixturesthereof, the WHSV is desirably at least about 20 hr⁻¹ and more desirablyfrom about 20 hr⁻¹ to about 300 hr⁻¹.

Oxygenate conversion should be maintained sufficiently high to avoid theneed for commercially unacceptable levels of feed recycling. While 100%oxygenate conversion is desired for the purpose of completely avoidingfeed recycle, a reduction in unwanted by-products is observed frequentlywhen the conversion is about 98% or less. Since recycling up to as muchas about 50% of the feed can be commercially acceptable, conversionrates from about 50% to about 98% are desired. According to oneembodiment, conversion rates are maintained in this range—50% to about98%—using a number of methods familiar to persons of ordinary skill inthe art. Examples include, but are not necessarily limited to, adjustingone or more of the following: reaction temperature; pressure; flow rate(weight hourly space velocity and/or gas superficial velocity); catalystrecirculation rate; reactor apparatus configuration; reactorconfiguration; feed composition; amount of liquid feed relative to vaporfeed; amount of recirculated catalyst; degree of catalyst regeneration;and other parameters which affect the conversion.

During the conversion of oxygenates to light olefins, carbonaceousdeposits accumulate on the catalyst used to promote the conversionreaction. At some point, the build up of these carbonaceous depositscauses a reduction in the capability of the catalyst to convert theoxygenate feed to light olefins. At this point, the catalyst ispartially deactivated. When a catalyst can no longer convert anoxygenate to an olefin product, the catalyst is considered to be fullydeactivated. As a step in the process of the present invention, aportion of the catalyst is withdrawn from the reactor apparatus and atleast a portion of the portion removed from the reactor is partially, ifnot fully, regenerated in a regenerator. By regeneration, it is meantthat the carbonaceous deposits are at least partially removed from thecatalyst. Desirably, the portion of the catalyst withdrawn from thereactor is at least partially deactivated. The remaining portion of thecatalyst in the reactor apparatus is recirculated without regeneration.The regenerated catalyst, with or without cooling, is then returned tothe reactor. Desirably, the rate of withdrawing the portion of thecatalyst for regeneration is from about 0.1% to about 99% of the rate ofthe catalyst exiting the reactor. More desirably, the rate is from about0.2% to about 50%, and, most desirably, from about 0.5% to about 5%.

According to an embodiment, the catalyst is regenerated in any number ofmethods—batch, continuous, semi-continuous, or a combination thereof.Continuous catalyst regeneration is a desired method. Desirably, thecatalyst is regenerated to a level of remaining coke from about 0.01 wt% to about 15 wt % of the weight of the catalyst.

The catalyst regeneration temperature should be from about 250° C. toabout 750° C., and desirably from about 500° C. to about 725° C. Thetemperature in the regenerator can be controlled by removing excessheat. Desirably, catalyst regeneration is carried out at least partiallydeactivated catalyst that has been stripped of most of readily removableorganic materials (organics) in a stripper or stripping chamber first.This stripping can be achieved by passing a stripping gas over the spentcatalyst at an elevated temperature. Gases suitable for strippinginclude steam, nitrogen, helium, argon, methane, CO₂, CO, hydrogen, andmixtures thereof. A preferred gas is steam. Gas hourly space velocity(GHSV, based on volume of gas to volume of catalyst and coke) of thestripping gas is from about 0.1 h⁻¹ to about 20,000 h⁻¹. Acceptabletemperatures of stripping are from about 250° C. to about 750° C., anddesirably from about 350° C. to about 675° C.

The process of the present invention for converting oxygenates to lightolefins employs a feed including an oxygenate. As used herein, the term“oxygenate” is defined to include, but is not necessarily limited to,hydrocarbons containing oxygen such as the following: aliphaticalcohols, ethers, carbonyl compounds (aldehydes, ketones, carboxylicacids, carbonates, and the like), and; mixtures thereof. The aliphaticmoiety desirably should contain in the range of from about 1–10 carbonatoms and more desirably in the range of from about 1–4 carbon atoms.Representative oxygenates include, but are not necessarily limited to,lower straight chain or branched aliphatic alcohols, and theirunsaturated counterparts. Examples of suitable oxygenates include, butare not necessarily limited to the following: methanol; ethanol;n-propanol; isopropanol; C₄–C₁₀ alcohols; methyl ethyl ether; dimethylether; diethyl ether; di-isopropyl ether; methyl formate; formaldehyde;di-methyl carbonate; methyl ethyl carbonate; acetone; and mixturesthereof. Desirably, the oxygenate used in the conversion reaction isselected from the group consisting of methanol, dimethyl ether andmixtures thereof. More desirably the oxygenate is methanol. The totalcharge of feed to the reactor apparatus can contain additionalcomponents, such as diluents.

One or more diluents can be fed to the reaction zone with theoxygenates, such that the total feed mixture comprises diluent in arange of from about 1 mol % and about 99 mol %. Diluents which can beemployed in the process include, but are not necessarily limited to,helium, argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen,water, paraffins, other hydrocarbons (such as methane), aromaticcompounds, and mixtures thereof. Desired diluents include, but are notnecessarily limited to, water and nitrogen.

The catalyst suitable for catalyzing the oxygenate-to-olefin conversionreaction of the present invention includes a molecular sieve andmixtures of molecular sieves. Molecular sieves can be zeolitic(zeolites) or non-zeolitic (non-zeolites). Useful catalysts can also beformed from mixtures of zeolitic and non-zeolitic molecular sieves.Desirably, the catalyst includes a non-zeolitic molecular sieve. Desiredmolecular sieves for use with the process of the present inventioninclude “small” and “medium” pore molecular sieves. “Small pore”molecular sieves are defined as molecular sieves with pores having adiameter of less than about 5.0 Angstroms. “Medium pore” molecularsieves are defined as molecular sieves with pores having a diameter fromabout 5.0 to about 10.0 Angstroms.

Molecular sieves are porous solids having pores of different sizes suchas zeolites or zeolite-type molecular sieves, carbons and oxides. Thereare amorphous and crystalline molecular sieves. Molecular sieves includenatural, mineral molecular sieves, or chemically formed, syntheticmolecular sieves that are typically crystalline materials containingsilica, and optionally alumina. The most commercially useful molecularsieves for the petroleum and petrochemical industries are known aszeolites. A zeolite is an aluminosilicate having an open frameworkstructure that usually carries negative charges. This negative chargewithin portions of the framework is a result of an Al³⁺ replacing aSi⁴⁺. Cations counter-balance these negative charges preserving theelectroneutrality of the framework, and these cations are exchangeablewith other cations and/or protons. Synthetic molecular sieves,particularly zeolites, are typically synthesized by mixing sources ofalumina and silica in a strongly basic aqueous media, often in thepresence of a structure directing agent or templating agent. Thestructure of the molecular sieve formed is determined in part bysolubility of the various sources, silica-to-alumina ratio, nature ofthe cation, synthesis temperature, order of addition, type of templatingagent, and the like.

A zeolite is typically formed from corner sharing the oxygen atoms of[SiO₄] and [AlO₄] tetrahedra or octahedra. Zeolites in general have aone-, two- or three-dimensional crystalline pore structure havinguniformly sized pores of molecular dimensions that selectively adsorbmolecules that can enter the pores, and exclude those molecules that aretoo large. The pore size, pore shape, interstitial spacing or channels,composition, crystal morphology and structure are a few characteristicsof molecular sieves that determine their use in various hydrocarbonadsorption and conversion processes.

There are many different types of zeolites well known to convert afeedstock, especially oxygenate containing feedstock, into one or moreolefin(s). For example, U.S. Pat. No. 5,367,100 describes the use of awell known zeolite, ZSM-5, to convert methanol into olefin(s); U.S. Pat.No. 4,062,905 discusses the conversion of methanol and other oxygenatesto ethylene and propylene using crystalline aluminosilicate zeolites,for example Zeolite T, ZK5, erionite and chabazite; and U.S. Pat. No.4,079,095 describes the use of ZSM-34 to convert methanol to hydrocarbonproducts such as ethylene and propylene.

Crystalline aluminophosphates, ALPO₄, formed from corner sharing [AlO₂]and [PO₂] tetrahedra linked by shared oxygen atoms are described in U.S.Pat. No. 4,310,440 to produce light olefin(s) from an alcohol. Metalcontaining aluminophosphate molecular sieves, MeAPO's and ElAPO's, havebeen also described to convert alcohols into olefin(s). MeAPO's have a[MeO₂], [AlO₂] and [PO₂] tetrahedra microporous structure, where Me is ametal source having one or more of the divalent elements Co, Fe, Mg, Mnand Zn, and trivalent Fe from the Periodic Table of Elements. ElAPO'shave an [ElO₂], [AlO₂] and [PO₂] tetrahedra microporous structure, whereEl is a metal source having one or more of the elements As, B, Be, Ga,Ge, Li, Ti and Zr. MeAPO's and ElAPO's are typically synthesized by thehydrothermal crystallization of a reaction mixture of a metal source, analuminum source, a phosphorous source and a templating agent. Thepreparation of MeAPO's and ElAPO's are found in U.S. Pat. Nos.4,310,440, 4,500,651, 4,554,143, 4,567,029, 4,752,651, 4,853,197,4,873,390 and 5,191,141.

One of the most useful molecular sieves for converting methanol toolefin(s) are those ELAPO's or MeAPO's where the metal source issilicon, often a fumed, colloidal or precipitated silica. Thesemolecular sieves are known as silicoaluminophosphate molecular sieves.Silicoaluminophosphate (SAPO) molecular sieves contain athree-dimensional microporous crystalline framework structure of [SiO₂],[AlO₂] and [PO₂] corner sharing tetrahedral units. SAPO synthesis isdescribed in U.S. Pat. No. 4,440,871, which is herein fully incorporatedby reference. SAPO is generally synthesized by the hydrothermalcrystallization of a reaction mixture of silicon-, aluminum- andphosphorus-sources and at least one templating agent. Synthesis of aSAPO molecular sieve, its formulation into a SAPO catalyst, and its usein converting a hydrocarbon feedstock into olefin(s), particularly wherethe feedstock is methanol, are shown in U.S. Pat. Nos. 4,499,327,4,677,242, 4,677,243, 4,873,390, 5,095,163, 5,714,662 and 6,166,282, allof which are herein fully incorporated by reference.

Molecular sieves have various chemical and physical, framework,characteristics. Molecular sieves have been well classified by theStructure Commission of the International Zeolite Association accordingto the rules of the IUPAC Commission on Zeolite Nomenclature. Aframework-type describes the connectivity, topology, of thetetrahedrally coordinated atoms constituting the framework, and makingan abstraction of the specific properties for those materials.Framework-type zeolite and zeolite-type molecular sieves for which astructure has been established, are assigned a three letter code and aredescribed in the Atlas of Zeolite Framework Types, 5th edition,Elsevier, London, England (2001), which is herein fully incorporated byreference.

Non-limiting examples of these molecular sieves are the small poremolecular sieves of framework-type selected from the group consisting ofAEI, AFT, APC, ATN, ATT, ATV, AWW, BIK, CAS, CHA, CHI, DAC, DDR, EDI,ERI, GOO, KFI, LEV, LOV, LTA, MON, PAU, PHI, RHO, ROG, THO, andsubstituted forms thereof; the medium pore molecular sieves offramework-type selected from the group consisting of AFO, AEL, EUO, HEU,FER, MEL, MFI, MTW, MTT, TON, and substituted forms thereof; and thelarge pore molecular sieves of framework-type selected from the groupconsisting of EMT, FAU, and substituted forms thereof. Other molecularsieves include framework-types selected from the group consisting ofANA, BEA, CFI, CLO, DON, GIS, LTL, MER, MOR, MWW and SOD. Non-limitingexamples of a preferred molecular sieve framework-types, particularlyfor converting an oxygenate containing feedstock into olefin(s), areselected from the group consisting of AEL, AFY, BEA, CHA, EDI, FAU, FER,GIS, LTA, LTL, MER, MFI, MOR, MTT, MWW, TAM and TON. In one preferredembodiment, the molecular sieve of the invention has an AEI topology ora CHA topology, or a combination thereof, most preferably a CHAtopology.

Molecular sieve materials all have 3-dimensional, four-connectedframework structure of corner-sharing TO₄ tetrahedra, where T is anytetrahedrally coordinated cation. These molecular sieves are typicallydescribed in terms of the size of the ring that defines a pore, wherethe size is based on the number of T atoms in the ring. Otherframework-type characteristics include the arrangement of rings thatform a cage, and when present, the dimension of channels, and the spacesbetween the cages. See van Bekkum, et al., Introduction to ZeoliteScience and Practice, Second Completely Revised and Expanded Edition,Volume 137, pages 1–67, Elsevier Science, B.V., Amsterdam, Netherlands(2001).

The small, medium and large pore molecular sieves have from a 4-ring toa 12-ring or greater framework-type. In a preferred embodiment, thezeolitic molecular sieves have 8-, 10- or 12-ring structures or largerand an average pore size in the range of from about 3 Å to 15 Å. In themost preferred embodiment, the molecular sieves of the invention,preferably silicoaluminophosphate molecular sieves have 8-rings and anaverage pore size less than about 5 Å, preferably in the range of from 3Å to about 5 Å, more preferably from 3 Å to about 4.5 Å, and mostpreferably from 3.5 Å to about 4.2 Å.

Molecular sieves, particularly zeolitic and zeolitic-type molecularsieves, preferably have a molecular framework of one, preferably two ormore corner-sharing [TO₄] tetrahedral units, more preferably, two ormore [SiO₄], [AlO₄] and/or [PO₄] tetrahedral units, and most preferably[SiO₄], [AlO₄] and [PO₄] tetrahedral units. These silicon, aluminum, andphosphorous based molecular sieves and metal containing silicon,aluminum and phosphorous based molecular sieves have been described indetail in numerous publications including for example, U.S. Pat. No.4,567,029 (MeAPO where Me is Mg, Mn, Zn, or Co), U.S. Pat. No. 4,440,871(SAPO), European Patent Application EP-A-0 159 624 (ELAPSO where El isAs, Be, B, Cr, Co, Ga, Ge, Fe, Li, Mg, Mn, Ti or Zn), U.S. Pat. No.4,554,143 (FeAPO), U.S. Pat. No. 4,822,478, 4,683,217, 4,744,885(FeAPSO), EP-A-0 158 975 and U.S. Pat. No. 4,935,216 (ZnAPSO, EP-A-0 161489 (CoAPSO), EP-A-0 158 976 (ELAPO, where EL is Co, Fe, Mg, Mn, Ti orZn), U.S. Pat. No. 4,310,440 (AlPO₄), EP-A-0 158 350 (SENAPSO), U.S.Pat. No. 4,973,460 (LiAPSO), U.S. Pat. No. 4,789,535 (LiAPO), U.S. Pat.No. 4,992,250 (GeAPSO), U.S. Pat. No. 4,888,167 (GeAPO), U.S. Pat. No.5,057,295 (BAPSO), U.S. Pat. No. 4,738,837 (CrAPSO), U.S. Pat. Nos.4,759,919, and 4,851,106 (CrAPO), U.S. Pat. Nos. 4,758,419, 4,882,038,5,434,326 and 5,478,787 (MgAPSO), U.S. Pat. No. 4,554,143 (FeAPO), U.S.Pat. No. 4,894,213 (AsAPSO), U.S. Pat. No. 4,913,888 (AsAPO), U.S. Pat.Nos. 4,686,092, 4,846,956 and 4,793,833 (MnAPSO), U.S. Pat. Nos.5,345,011 and 6,156,931 (MnAPO), U.S. Pat. No. 4,737,353 (BeAPSO), U.S.Pat. No. 4,940,570 (BeAPO), U.S. Pat. Nos. 4,801,309, 4,684,617 and4,880,520 (TiAPSO), U.S. Pat. Nos. 4,500,651, 4,551,236 and 4,605,492(TiAPO), U.S. Pat. Nos. 4,824,554, 4,744,970 (CoAPSO), U.S. Pat. No.4,735,806 (GaAPSO) EP-A-0 293 937 (QAPSO, where Q is framework oxideunit [QO₂]), as well as U.S. Pat. Nos. 4,567,029, 4,686,093, 4,781,814,4,793,984, 4,801,364, 4,853,197, 4,917,876, 4,952,384, 4,956,164,4,956,165, 4,973,785, 5,241,093, 5,493,066 and 5,675,050, all of whichare herein fully incorporated by reference.

Other molecular sieves include those described in EP-0 888 187 B1(microporous crystalline metallophosphates, SAPO₄ (UIO-6)), U.S. Pat.No. 6,004,898 (molecular sieve and an alkaline earth metal), U.S. patentapplication Ser. No. 09/511,943 filed Feb. 24, 2000 (integratedhydrocarbon co-catalyst), PCT WO 01/64340 published Sep. 7, 2001(thoriumcontaining molecular sieve), and R. Szostak, Handbook of MolecularSieves, Van Nostrand Reinhold, New York, N.Y. (1992), which are allherein fully incorporated by reference.

The more preferred silicon, aluminum and/or phosphorous containingmolecular sieves, and aluminum, phosphorous, and optionally silicon,containing molecular sieves include aluminophosphate (ALPO) molecularsieves and silicoaluminophosphate (SAPO) molecular sieves andsubstituted, preferably metal substituted, ALPO and SAPO molecularsieves. The most preferred molecular sieves are SAPO molecular sieves,and metal substituted SAPO molecular sieves. In an embodiment, the metalis an alkali metal of Group IA of the Periodic Table of Elements, analkaline earth metal of Group IIA of the Periodic Table of Elements, arare earth metal of Group IIIB, including the Lanthanides: lanthanum,cerium, praseodymium, neodymium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium;and scandium or yttrium of the Periodic Table of Elements, a transitionmetal of Groups IVB, VB, VIB, VIIB, VIIIB, and IB of the Periodic Tableof Elements, or mixtures of any of these metal species. In one preferredembodiment, the metal is selected from the group consisting of Co, Cr,Cu, Fe, Ga, Ge, Mg, Mn, Ni, Sn, Ti, Zn and Zr, and mixtures thereof. Inanother preferred embodiment, these metal atoms discussed above areinserted into the framework of a molecular sieve through a tetrahedralunit, such as [MeO₂], and carry a net charge depending on the valencestate of the metal substituent. For example, in one embodiment, when themetal substituent has a valence state of +2, +3, +4, +5, or +6, the netcharge of the tetrahedral unit is between −2 and +2.

In one embodiment, the molecular sieve, as described in many of the U.S.patents mentioned above, is represented by the empirical formula, on ananhydrous basis:mR:(M_(x)Al_(y)P_(z))O₂wherein R represents at least one templating agent, preferably anorganic templating agent; m is the number of moles of R per mole of(M_(x)Al_(y)P_(z))O₂ and m has a value from 0 to 1, preferably 0 to 0.5,and most preferably from 0 to 0.3; x, y, and z represent the molefraction of Al, P and M as tetrahedral oxides, where M is a metalselected from one of Group IA, IIA, IB, IIIB, IVB, VB, VIB, VIIB, VIIIBand Lanthanide's of the Periodic Table of Elements, preferably M isselected from one of the group consisting of Co, Cr, Cu, Fe, Ga, Ge, Mg,Mn, Ni, Sn, Ti, Zn and Zr. In an embodiment, m is greater than or equalto 0.2, and x, y and z are greater than or equal to 0.01. In anotherembodiment, m is greater than 0.1 to about 1, x is greater than 0 toabout 0.25, y is in the range of from 0.4 to 0.5, and z is in the rangeof from 0.25 to 0.5, more preferably m is from 0.15 to 0.7, x is from0.01 to 0.2, y is from 0.4 to 0.5, and z is from 0.3 to 0.5.

Non-limiting examples of SAPO and ALPO molecular sieves of the inventioninclude one or a combination of SAPO-5, SAPO-8, SAPO-11, SAPO-16,SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-36, SAPO-37,SAPO-40, SAPO-41, SAPO-42, SAPO-44 (U.S. Pat. No. 6,162,415), SAPO-47,SAPO-56, ALPO-5, ALPO-11, ALPO-18, ALPO-31, ALPO-34, ALPO-36, ALPO-37,ALPO-46, and metal containing molecular sieves thereof. The morepreferred zeolite-type molecular sieves include one or a combination ofSAPO-18, SAPO-34, SAPO-35, SAPO-44, SAPO-56, ALPO-18 and ALPO-34, evenmore preferably one or a combination of SAPO-18, SAPO-34, ALPO-34 andALPO-18, and metal containing molecular sieves thereof, and mostpreferably one or a combination of SAPO-34 and ALPO-18, and metalcontaining molecular sieves thereof.

In an embodiment, the molecular sieve is an intergrowth material havingtwo or more distinct phases of crystalline structures within onemolecular sieve composition. In particular, intergrowth molecular sievesare described in the combination of U.S. patent application Ser. No.09/924,016 filed Aug. 7, 2001 and PCT WO 98/15496 published Apr. 16,1998, both of which are herein fully incorporated by reference. Inanother embodiment, the molecular sieve comprises at least oneintergrown phase of AEI and CHA framework-types. For example, SAPO-18,ALPO-18 and RUW-18 have an AEI framework-type, and SAPO-34 has a CHAframework-type.

The synthesis of molecular sieves is described in many of the referencesdiscussed above. Generally, molecular sieves are synthesized by thehydrothermal crystallization of one or more of a source of aluminum, asource of phosphorous, a source of silicon, a templating agent, and ametal containing compound. Typically, a combination of sources ofsilicon, aluminum and phosphorous, optionally with one or moretemplating agents and/or one or more metal containing compounds areplaced in a sealed pressure vessel, optionally lined with an inertplastic such as polytetrafluoroethylene, and heated, under acrystallization pressure and temperature, until a crystalline materialis formed, and then recovered by filtration, centrifugation and/ordecanting.

In a preferred embodiment the molecular sieves are synthesized byforming a reaction product of a source of silicon, a source of aluminum,a source of phosphorous, an organic templating agent, preferably anitrogen containing organic templating agent, and one or more polymericbases. This particularly preferred embodiment results in the synthesisof a silicoaluminophosphate crystalline material that is then isolatedby filtration, centrifugation and/or decanting.

Non-limiting examples of silicon sources include silicates, fumedsilica, for example, Aerosil-200 available from Degussa Inc., New York,N.Y., and CAB-O-SIL M-5, silicon compounds such as tetraalkylorthosilicates, for example, tetramethyl orthosilicate (TMOS) andtetraethylsilicate (TEOS), colloidal silicas or aqueous suspensionsthereof, for example Ludox-HS-40 sol available from E.I. du Pont deNemours, Wilmington, Del., silicic acid, alkali-metal silicate, or anycombination thereof. The preferred source of silicon is a silica sol.

Non-limiting examples of aluminum sources include aluminum-containingcompositions such as aluminum alkoxides, for example aluminumisopropoxide, aluminum phosphate, aluminum hydroxide, sodium aluminate,pseudo-boehmite, gibbsite and aluminum trichloride, or any combinations.thereof. A preferred source of aluminum is pseudo-boehmite, particularlywhen producing a silicoaluminophosphate molecular sieve.

Non-limiting examples of phosphorus sources, which can also includealuminum-containing phosphorous compositions, includephosphorus-containing, inorganic or organic, compositions such asphosphoric acid, organic phosphates such as triethyl phosphate, andcrystalline or amorphous aluminophosphates such as ALPO₄, phosphorussalts, or combinations thereof. The preferred source of phosphorus isphosphoric acid, particularly when producing a silicoaluminophosphate.

Templating agents are generally compounds that contain elements of GroupVA of the Periodic Table of Elements, particularly nitrogen, phosphorus,arsenic and antimony, more preferably nitrogen or phosphorous, and mostpreferably nitrogen. Typical templating agents of Group VA of thePeriodic Table of elements also contain at least one alkyl or arylgroup, preferably an alkyl or aryl group having from 1 to 10 carbonatoms, and more preferably from 1 to 8 carbon atoms. The preferredtemplating agents are nitrogen-containing compounds such as amines andquaternary ammonium compounds.

The quaternary ammonium compounds, in one embodiment, are represented bythe general formula R₄N⁺, where each R is hydrogen or a hydrocarbyl orsubstituted hydrocarbyl group, preferably an alkyl group or an arylgroup having from 1 to 10 carbon atoms. In one embodiment, thetemplating agents include a combination of one or more quaternaryammonium compound(s) and one or more of a mono-, di- or tri-amine.

Non-limiting examples of templating agents include tetraalkyl ammoniumcompounds including salts thereof such as tetramethyl ammonium compoundsincluding salts thereof, tetraethyl ammonium compounds including saltsthereof, tetrapropyl ammonium including salts thereof, andtetrabutylammonium including salts thereof, cyclohexylamine, morpholine,di-n-propylamine (DPA), tripropylamine, triethylamine (TEA),triethanolamine, piperidine, cyclohexylamine, 2-methylpyridine,N,N-dimethylbenzylamine, N,N-diethylethanolamine, dicyclohexylamine,N,N-dimethylethanolamine, choline, N,N′-dimethylpiperazine,1,4-diazabicyclo(2,2,2)octane, N′,N′,N,N-tetramethyl-(1,6)hexanediamine, N-methyldiethanolamine,N-methyl-ethanolamine, N-methyl piperidine, 3-methyl-piperidine,N-methylcyclohexylamine, 3-methylpyridine, 4-methyl-pyridine,quinuclidine, N,N′-dimethyl-1,4-diazabicyclo(2,2,2) octane ion;di-n-butylamine, neopentylamine, di-n-pentylamine, isopropylamine,t-butyl-amine, ethylenediamine, pyrrolidine, and 2-imidazolidone.

The preferred templating agent or template is a tetraethylammoniumcompound, such as tetraethyl ammonium hydroxide (TEAOH), tetraethylammonium phosphate, tetraethyl ammonium fluoride, tetraethyl ammoniumbromide, tetraethyl ammonium chloride and tetraethyl ammonium acetate.The most preferred templating agent is tetraethyl ammonium hydroxide andsalts thereof, particularly when producing a silicoaluminophosphatemolecular sieve. In one embodiment, a combination of two or more of anyof the above templating agents is used in combination with one or moreof a silicon-, aluminum-, and phosphorous-source, and a polymeric base.

The molecular sieve can also be incorporated into a solid composition,preferably solid particles, in which the molecular sieve is present inan amount effective to catalyze the desired conversion reaction. Thesolid particles can include a catalytically effective amount of themolecular sieve and matrix material, preferably at least one of a fillermaterial and a binder material, to provide a desired property orproperties, e.g., desired catalyst dilution, mechanical strength and thelike, to the solid composition. Such matrix materials are often to someextent porous in nature and often have some nonselective catalyticactivity to promote the formation of undesired products and may or maynot be effective to promote the desired chemical conversion. Suchmatrix, e.g., filler and binder, materials include, for example,synthetic and naturally occurring substances, metal oxides, clays,silicas, aluminas, silica-aluminas, silica-magnesias, silica-zirconias,silica-thorias, silica-beryllias, silica-titanias,silica-alumina-thorias, silica-aluminazirconias, and mixtures of thesematerials.

The solid catalyst composition preferably comprises about 1% to about99%, more preferably about 5% to about 90%, and still more preferablyabout 10% to about 80%, by weight of molecular sieve; and an amount ofabout 1% to about 99%, more preferably about 5% to about 90%, and stillmore preferably about 10% to about 80%, by weight of matrix material.

The preparation of solid catalyst compositions, e.g., solid particles,comprising the molecular sieve and matrix material, is conventional andwell known in the art and, therefore, is not discussed in detail here.

The catalyst can further contain binders, fillers, or other material toprovide better catalytic performance, attrition resistance,regenerability, and other desired properties. Desirably, the catalyst isfluidizable under the reaction conditions. The catalyst should haveparticle sizes of from about 1μ to about 3,000μ, desirably from about 5μto about 300μ, and more desirably from about 5μ to about 200μ. Thecatalyst can be subjected to a variety of treatments to achieve thedesired physical and chemical characteristics. Such treatments include,but are not necessarily limited to, calcination, ball milling, milling,grinding, spray drying, hydrothermal treatment, acid treatment, basetreatment, and combinations thereof.

As additional methods for controlling the heat generated by theconversion reaction and, subsequently, the temperature differential inthe reactor, the present invention can include one or more or all of thefollowing steps: providing a portion of the oxygenate portion of thefeed to the reactor in a liquid form; providing at least a portion ofthe diluent to the reactor in a liquid form; and providing non-reactivesolids to the reactor apparatus.

When a portion of the feed is provided in a liquid form, the liquidportion of the feed can be either oxygenate, diluent or a mixture ofboth. The liquid portion of the feed can be directly injected into thereactor, or entrained or otherwise carried into the reactor with thevapor portion of the feed or a suitable carrier gas/diluent. Byproviding a portion of the feed (oxygenate and/or diluent) in the liquidphase, the temperature differential in the reactor can be furthercontrolled. The exothermic heat of reaction of oxygenate conversion ispartially absorbed by the endothermic heat of vaporization of the liquidportion of the feed. Controlling the proportion of liquid feed to vaporfeed fed to the reactor thus allows control of the temperaturedifferential in the reactor. Introduction of liquid feed to the reactoracts in concert with the recirculation of catalyst and non-reactivesolids, providing another independent variable to improve overallcontrol of the temperature in the reactor.

The amount of feed provided in a liquid form, whether fed separately orjointly with the vapor feed, is from about 0.1 wt. % to about 85 wt. %of the total oxygenate content plus diluent in the feed. More desirably,the range is from about 1 wt. % to about 75 wt. % of the total oxygenateplus diluent feed, and most desirably the range is from about 5 wt. % toabout 65 wt. %. The liquid and vapor portions of the feed can be thesame composition, or can contain varying proportions of the same ordifferent oxygenates and same or different diluents. One particularlyeffective liquid diluent is water, due to its relatively high heat ofvaporization, which allows for a high impact on the reactor temperaturedifferential with a relatively small rate. Other useful diluents aredescribed above. Proper selection of the temperature and pressure of anyappropriate oxygenate and/or diluent being fed to the reactor willensure at least a portion is in the liquid phase as it enters thereactor and/or comes into contact with the catalyst or a vapor portionof the feed and/or diluent.

Optionally, the liquid fraction of the feed can be split into portionsand introduced to the inlet zone and at a multiplicity of locationsalong the length of the reactor. According to one embodiment, this isdone with either the oxygenate feed, the diluent or both. Typically,this is done with the diluent portion of the feed. Another option is toprovide a nozzle which introduces the total liquid fraction of the feedto the inlet zone or reactor in a manner such that the nozzle formsliquid droplets of an appropriate size distribution which, whenentrained with the gas and solids introduced to the inlet zone orreactor, vaporize gradually along the length of the reactor. Either ofthese arrangements or a combination thereof can be used to bettercontrol the temperature differential in the reactor. The means ofintroducing a multiplicity of liquid feed points in a reactor ordesigning a liquid feed nozzle to control droplet size distribution iswell known in the art and is not discussed here, except in relation tointroduction of the liquid fuel to the regenerator.

Non-reactive solids which contain no molecular sieve are mixed with thecatalyst solids, and used in the reactor, and recirculated to thereactor and regenerator in one embodiment. These non-reactive solidshave the same capability as the catalyst to provide inertial mass tocontrol temperature rise in the reactor, but are substantially inert forthe purposes of oxygenate conversion. Suitable materials for use asnon-reactive solids are metals, metal oxides, and mixtures thereof.Particularly suitable materials are those used as matrices for thecatalyst formulation, e.g., fillers and binders such as silicas andaluminas, among others, and mixtures thereof. Desirably, thenon-reactive solids should have a heat capacity of from about 0.05 toabout 1 cal/g-° C., more preferably from about 0.1 to about 0.8 cal/g-°C., and most preferably from about 0.1 to about 0.5 cal/g-° C. Further,desirably, the mass proportion of non-reactive solids to catalyst isfrom about 0.01 to about 10, more desirably from about 0.05 to about 5.

One skilled in the art will appreciate that the non-reactive solids canalso be regenerated with the catalyst in the manner described above.

The process of the present invention is desirably carried out in areactor apparatus which comprises an inlet zone, a reaction zone, and adisengaging zone. In one embodiment, the superficial gas velocity in thereaction zone is above about 1 m/s and preferrably above about 2 m/s.When the process-of the present invention is conducted in this type ofreactor apparatus, at least a portion of the catalyst/solids isrecirculated from the disengaging zone to the inlet zone to maintain thereactor at near isothermal conditions. At least a portion of the vaporfeed then mixes with the catalyst/solids in the inlet zone and isdirected to the reaction zone in which the oxygenate to olefinconversion reaction takes place. Optionally, a liquid feed and/ordiluent portion of the total feed or various sub-portions thereof can bedirected to the inlet zone and/or to one or more locations in thereaction zone. With this apparatus, the catalyst/solids can berecirculated either inside the reactor apparatus or external to therector apparatus as the catalyst/solids are recirculated from thedisengaging zone to the inlet zone and/or the reaction zone. As alsodescribed, an additional portion of the catalyst/solids can optionallybe removed from the reactor apparatus and sent to a regenerator toregenerate the catalyst. Catalyst/solids from the regenerator can bereturned to any of the three zones, or can be directed to a conduitwhich serves to recirculate the catalyst/solids from the disengagingzone to the inlet zone or reaction zone.

A preferred embodiment of a reactor system for the present invention isa circulating fluid bed reactor with continuous regeneration, similar toa modern fluid catalytic cracker. Fixed beds are not practical for theprocess because oxygenate to olefin conversion is a highly exothermicprocess which requires several stages with intercoolers or other coolingdevices. The reaction also results in a high pressure drop due to theproduction of low pressure, low density gas.

It is important for the reactor to be designed such that a relativelyhigh average level of coke on catalyst (or carbon atoms per catalystactive site) is maintained—an amount greater than about 1.5 wt %,preferably in the range of from about 2 wt % to about 30 wt %, mostpreferably in the range of from about 2 wt % to about 20 wt %. If thereactor is a high velocity fluidized bed reactor (sometimes referred toas a riser reactor), then a portion of the catalyst exiting the top ofthe reactor must be returned to the reactor inlet via a catalystrecirculation conduit. This is different from a typical Fluid CatalyticCracker (FCC) riser reactor, where all or most of the catalyst exitingthe top of the reactor is sent to the regenerator. The return of cokedcatalyst directly to the reactor, without regenerating the cokedcatalyst, allows the average coke level of the catalyst in the reactorto build up to a preferred level. By adjusting the ratio of the flow ofthe coked catalyst between the regenerator and the reactor, a preferredlevel of coking, or “desirable carbonaceous deposits,” can bemaintained.

If the fluidized bed reactor is designed with low superficial gasvelocities, below about 2 m/sec, then cyclones alone can be used toreturn catalyst fines to the fluidized bed reaction zone. Such reactorsgenerally have high recirculation rates of solids within the fluidizedbed, which allows the coke level on the catalyst to build to a preferredlevel. Similarly, in one embodiment, a regenerator will operate with agas superficial velocity of or below about 2 m/s, preferably greaterthan about 1 m/s. A preferred embodiment of a reactor apparatuscomprising a riser for use in the present invention is depictedgenerally as 10 in the FIGURE. A methanol feed 12 is at least partiallyvaporized in a preheater (not shown). The methanol feed is mixed withregenerated catalyst 28 and coked catalyst 22 at the bottom of the riserreactor 14. An inert gas and/or steam can be used to dilute themethanol, lift the catalyst streams 22 and 28, and keep pressureinstrument lines clear of catalyst. This inert gas and/or steam mixeswith the methanol and catalyst in the reactor 14. The reaction isexothermic, and a preferred reaction temperature, in the range of fromabout 300° C. to about 500° C., is maintained by removing heat. Heat canbe removed by any suitable means, including but not necessarily limitedto cooling the reactor with a catalyst cooler (not shown), feeding someof the methanol as a liquid, cooling the catalyst feed to the reactor,or any combination of these methods.

The reactor effluent 16, containing products, coked catalyst, diluents,and unconverted feed, should flow to a disengaging zone 18. In the.disengaging zone 18, coked catalyst is separated from the gaseousmaterials by means of gravity and/or cyclone separators. A portion ofthe coked catalyst 22 is returned to the reactor inlet. The portion ofcoked catalyst 22 to be regenerated is first sent to a stripping zone29, where steam or other inert gas is used to recover adsorbedhydrocarbons from the catalyst. Stripped spent coked catalyst 23 shouldflow to the regenerator 24. The portion of the catalyst sent to theregenerator 24 should be contacted with a regeneration medium,preferably a gas comprising oxygen, e.g., air, 30 introduced throughregeneration medium inlet 31, at temperatures, pressures, and residencetimes that are capable of burning coke off of the catalyst and down to alevel of less than about 0.5 wt %. The preferred temperature in theregenerator is in the range of from about 550° C. to about 725° C., apreferred oxygen concentration in the gas leaving the regenerator is inthe range of from about 0.1 vol % to about 5 vol %, and a preferredcatalyst residence time is in the range of from about 1 to about 100minutes.

The burning off of coke is exothermic. The temperature can be maintainedat a suitable level by any acceptable method, including but not limitedto feeding cooler gas, cooling the catalyst in the regenerator with acat cooler 26, or a combination of these methods.

The regenerated catalyst 28 is sent to the reactor 14, where it mixeswith the recirculated coked catalyst 22 and the methanol feed 12. Theregenerated catalyst 28 can be lifted to the reactor 14 by means of aninert gas, steam, or methanol vapor introduced via lift gas line 25. Theprocess should repeat itself in a continuous or semi-continuous manner.The hot reactor product gases 20 should be cooled, the water byproductcondensed and collected, and the desired olefin product gases recoveredfor further processing.

In order to determine the level of coke in the reactor and in theregenerator, small samples of catalyst periodically can be withdrawnfrom various points in the recirculating system for measurement ofcarbon content. The reaction parameters can be adjusted accordingly.

As noted above, there are certain situations where it is desirable toadd supplemental heat to the reactor/regenerator system. When startingfrom at or near ambient temperature, the regeneration zone 24 isinitially heated with hot air, by combusting a gaseous or liquidstarting fuel in auxiliary burner 32 with regeneration medium 30introduced through regeneration medium (air) inlet 31. In oneembodiment, the combustion occurs at or upstream of the regenerationmedium inlet. As long as there is sufficient catalyst, say, up to alevel 33, in the regeneration zone 24 to cover the heating fuel inlet34, and provided that the temperature in zone 24 is above theautoignition temperature of the liquid fuel, then the heating fuel,e.g., a normally liquid fuel, can be injected into the regeneration zone24 through one or more nozzles 35. The liquid heating fuel will reactwith the air, thereby adding heat to the regenerator.

In one embodiment, a second, less dense fluidized portion of thecatalyst is maintained between level 33 and level 36 of the regenerationzone 24.

When the regenerator zone 24 is already above the autoignitiontemperature of the heating fuel, the heating fuel can be introducedwithout first using the auxiliary burner 32.

The flow rate of heating fuel can be varied according to the amount ofheat required to bring the temperature of the catalyst and reactants toa temperature capable of initiating and sustaining the oxygenateconversion. Heated catalyst can be circulated within plural riserssimultaneously, if necessary, to effect rapid start-up.

The heating fuel employed for the present invention exhibits certainproperties. It must be clean with low, if any, sulfur, nitrogen or metalcompound impurities. Typically, such impurities are individually presentin amounts by weight of less than 100 wppm, 10 wppm, 1 wppm, or evenless than 0.5 wppm. Additionally, such heating fuel exhibits a lowautoignition temperature, typically, no greater than 371° C. (700° F.),e.g. 232° to 271° C. (450° to 520° F.). These temperatures can bereached in the regenerator zone 24 by operating the auxiliary burner 32alone. In order to avoid the formation of localized “hot spots” withinthe reactor apparatus, the heating fuel has a molecular weight of atleast 150, say at least 170, in order to promote a slow burn duringcombustion. The heating fuel can be a torch oil having the propertiesnoted above.

Paraffins having the properties described above and ranging from 12 to20 carbons are especially suited to use as the heating fuels used in thepresent invention and are preferably normally liquid, i.e., liquid underambient conditions, say, room temperature and atmospheric pressure.

A preferred embodiment employs as a heating fuel C₁₂ to C₂₀ linear ornormal paraffins. Especially preferred are liquid fuels which areprepared by treating a distillation cut by molecular exclusionchromatography to provide a product rich in normal paraffins. Suchmaterials are available from ExxonMobil Chemical of Houston, Tex. underthe name Norpar®. Norpar® fluids all have a flash point above 140° F.and are normal paraffins which have been isolated from kerosene. Norpar®12 and Norpar® 14 are especially suited to use in the present invention.The number refers to the average carbon number of the material.

Another preferred embodiment employs as a heating fuel C₁₂ to C₂₀branched paraffins. Such materials are available from ExxonMobilChemical under the name Isopar®. Isopar® 12 (containing C₁₂hydrocarbons) and Isopar® 14 (containing C₁₄ hydrocarbons) areespecially suited to use in the present invention. The number refers tothe average carbon number of the material.

Still another preferred embodiment employs as a heating fueldearomatized aliphatic fluids available from ExxonMobil Chemical, suchas Exxsol® D80 (containing C₁₂–C₁₃ hydrocarbons), Exxsol® D100(containing C₁₃–C₁₄ hydrocarbons), Exxsol® D110 (containing C₁₄–C₁₆hydrocarbons), Exxsol® D120 (containing C₁₄–C₁₈ hydrocarbons) andExxsol®D140 (containing C₁₆–C₁₉ hydrocarbons).

Persons of ordinary skill in the art will recognize that manymodifications can be made to the present invention without departingfrom the spirit and scope of the present invention. The embodimentsdescribed herein are meant to be illustrative only and should not betaken as limiting the invention, which is defined by the followingclaims.

1. A process for adding heat to a reactor system having an oxygenate toolefin reaction zone and a catalyst regeneration zone wherein catalystis cycled from the reaction zone to the regeneration zone and from theregeneration zone to the reaction zone, the process comprising: cyclingcatalyst from said reaction zone to said regeneration zone; fluidizingcatalyst in the regeneration zone in the presence of an oxygencontaining gas; heating the catalyst in said regeneration zone to afirst temperature of at least about 225° C. (437° F.); introducing aliquid heating fuel into the regeneration zone wherein the liquidbeating fuel has about 500 wppm or less of sulfur and has about 200 wppmor less nitrogen and an autoignition temperature no greater than about482° C. (900° F.); imparting sufficient heat content within saidregeneration zone to initiate and sustain ignition of said liquidheating fuel to thereby provide a further heated catalyst; and providingsaid further heated catalyst into the reaction zone by cycling saidfurther heated catalyst from said regeneration zone to said reactionzone in order for said further heated catalyst to heat said reactionzone to a temperature of at least 316° C. (600° F.).
 2. The process ofclaim 1 which further comprises: contacting said catalyst with anoxygenate feedstock under conditions sufficient to convert saidoxygenate to an olefin-rich product and said heating fuel has about 100wppm or less of sulfur and has about 100 ppmw or less nitrogen.
 3. Theprocess of claim 1 wherein said heating fuel contains a total of nogreater than 20 wppm of metal selected from the group consisting ofnickel and vanadium.
 4. A process for initially increasing thetemperature of a reactor system for making in a reaction zone an olefinproduct from an oxygenate feedstock in the presence of an oxygenate toolefin molecular sieve catalyst which process comprises: a) contactingat least a portion of the catalyst taken from said reaction zone with aregeneration medium in a regeneration tone; b) heating said regenerationzone to a first temperature of at least 225° C. (437° F.), c) feeding tosaid regeneration zone a liquid heating fuel having an autoignitiontemperature less than the first temperature and containing less than 500wppm sulfur and less than 200 wppm nitrogen, thereby causing the liquidheating fuel to ignite and provide a further healed catalyst; and d)circulating said further heated catalyst from said regeneration zone tothe reaction zone in order for said further heated catalyst to heat saidreaction zone to a temperature of at least 316° C. (600° F.).
 5. Theprocess of claim 4 which further comprises: a) additionally contactingthe feedstock in a reaction zone with said oxygenate to olefin molecularsieve catalyst including said heated catalyst, under conditionseffective to convert the feedstock into an olefin product stream.
 6. Theprocess of claim 4 wherein said heating fuel contains less than 100 ppmsulfur and less than 100 wppm nitrogen.